While everyone expected Iran to move quickly on implementing the P5+1 nuclear deal, US officials are alarmed at the alacrity of their compliance, saying they have “unreasonable expectations” that the West will implement their own side of the deal in a timely fashion.

With the next phase of the Iran nuclear deal beginning Sunday, some U.S. officials worry that Tehran has set unrealistic expectations for how quickly it can comply with the deal and end economic sanctions.

Iranian President Hassan Rouhani is impatient to downsize Iran’s nuclear hardware and thereby halt the sanctions on his country. Iran holds parliamentary elections on February 26, and Rouhani’s moderate faction might gain if the sanctions are history by then.

Rouhani is competing with hardliners who are casting doubt on when—and even whether—the promised sanctions relief will materialize, and who have recently raised tensions with the U.S. by convicting an American journalist of espionage and testing a ballistic missile in defiance of the United Nations.

In an interview on Iranian TV last week, the Iranian president said the sanctions could come off “one to two months” after Iran begins the process of implementing the nuclear deal. Sunday marks the official start to that process, on what the nuclear deal calls “adoption day,” leading to an unspecified “implementation day” when Iran’s actions have been verified and sanctions are halted as a reward.

Rouhani’s timeline may be wildly optimistic. Many nuclear experts—including Energy Department technical experts involved in the Iran talks—believe it could take Iran six months or more to complete the work required by the agreement. That work includes uninstalling and storing thousands of centrifuges, whose operation was capped under the deal; refashioning the core of a reactor at Arak to prevent it from producing plutonium; and reducing Iran’s stockpile of nuclear material by diluting it or shipping it out of the country.

“There’s a lot that Iran needs to do before it can actually get the sanctions relief that we’re offering in the deal,” said a senior administration official, who said the time frame is “at least months.”

Outside experts versed in the details of the nuclear deal were blunter.

“There’s no way they can do it properly or effectively” in a matter of weeks, says Robert Einhorn, a former Iran nuclear negotiator at the Obama State Department now with the Brookings Institution.

“Hopefully it doesn’t mean they’re planning to cut corners to get it done quickly,” added Einhorn, who said he has discussed the issue with both a senior Iranian official and with U.S. officials.

It’s not clear whether Iran could cheat its way to the deal’s implementation. Under the agreement signed by Tehran with the U.S. and five other world powers in July, international inspectors will oversee and verify that Iran has taken the initial steps limiting the scale of its nuclear program required before the other nations agree to lift sanctions that have stunted Iran’s economy.

“The Iranians may try to cut corners to help Rouhani politically, but I think we are in a very strong position to insist on vigorous compliance,” said Gary Samore, a former Obama White House official now with the Belfer Center for Science and International Affairs at Harvard University’s Kennedy School of Government.

Still, Rouhani’s rhetoric spotlights continuing political tension around the nuclear deal, and the urgency felt by the deal’s backers in Iran to deliver results as hard-liners attack the deal.

“Rouhani is responding to a lot of pressure that has come from the conservatives,” said Abbas Milani, director of the Iranian Studies program at Stanford University.

Rouhani is under high pressure to demonstrate that the nuclear deal will deliver swift and tangible benefits in return for reducing the scale of Iran’s atomic program.

Last month, four Iranian ministers sent Rouhani an unusual letter warning him that the country’s economy was on the brink of a “crisis.”

Rouhani says that the removal of sanctions will mean an economic rebound for Iran. But Iran’s top conservative newspaper has accused him of misleading the public about how long it will take for the sanctions to end, and even whether the U.S. and its negotiating partners—China, Russia, Great Britain, France and Germany—will ever permanently void them, Milani said.

Iran’s parliament ratified the deal last week, after a debate that featured vitriol and even physical threats against top Iranian negotiators from conservatives.

Iran’s top nuclear negotiator, Ali Akbar Salehi, told Iran’s parliament that one of its members said he should be buried in the concrete that will be used to disable the Arak reactor’s core.

While the American debate over the Iran deal has cooled since it became clear that Congress wouldn’t block the agreement, Iranian politics are still roiling in advance of February’s elections.

Last Sunday, Iran’s military tested a precision-guided ballistic missile in what the U.S. ambassador to the United Nations, Samantha Power, called a “clear violation” of U.N. sanctions.

Obama officials say the test did not violate the nuclear deal itself, but it has nevertheless riled the deal’s opponents in Congress. “This serious violation requires immediate action by the administration to deter Iran’s behavior,” Senate Foreign Relations Committee chairman Bob Corker said in a statement.

Also last Sunday, Iranian media reported that a court had convicted Washington Post correspondent Jason Rezaian of espionage. The details of his sentence have not been released. Rezian has already spent 14 months in jail.

Few experts believe that Iran’s hardliners can sabotage the nuclear deal, particularly given support for it from Iran’s ultimate authority, Supreme Leader Ali Khamenei.

But the February elections could affect the ever-shifting balance of power between Iran’s conservative and reformist wing. The February 26 vote will determine the makeup of both Iran’s 290-member parliament, or majlis, and its Council of Experts, the 86-member panel which chooses Iran’s Supreme Leader. That role looms particularly large given the 76-year-old Khamenei’s recent bout with an illness Iranian officials said was prostate cancer.

Milani noted that the elections aren’t entirely free—all candidates are pre-approved by the Supreme Leader. But, he said, they still have the potential to affect the country’s course.

“The elections will determine whether Rouhani and company can bank on the political capital that will come from this deal, and move the country out of the past,” Milani said.

Think about who gets rich off of the Venezuela regime-change agenda. It’s the same people that said we had to invade Iraq in order to prevent nuclear apocalypse. It’s the same people who said the world would stop turning on its axis if we didn’t carpet bomb Libya and Syria.